The long-term goals of this project are to develop a genetically engineered vascular graft by identifying and expressing genes that interfere with the development of vascular graft disease. The demand for clinical vascular graft material far exceeds the supply. Development of methods for genetic engineering of vascular tissue would significantly improve the supply of useful vascular graft material. Vascular gene delivery has tremendous promise to serve as both an investigational and a therapeutic tool to improve vascular graft performance. Transfer of genes into the vessel wall can be used to identify the roles of these genes in the development or regression of graft disease. Identification of gene products that prevent the progression or promote regression of graft disease may lead to the development of powerful gene-based therapies. Progress in genetic engineering of vascular tissue has been hindered by the technical limitations of gene transfer vectors, including now efficiency, brief duration of expression, inflammatory host reactions, and alterations in the arterial phenotype. The specific aims of this proposal, designed to address these limitations, are: 1) to improve the utility of first-generation adenoviral vectors by genetic modifications that decrease vector immunogenicity and by the adjunctive use of targeted immunosuppression to block immune cell activation that occurs via B7 and/or CD40 ligand signaling. These strategies should substantially prolong recombinant gene expression and decrease vascular wall inflammation associated with infusion of first-generation adenoviral vectors; 2) to test the ability of adeno-associated virus and vesicular stomatitis virus G protein-pseudotyped murine retroviral vectors to accomplish efficient and durable vascular gene transfer without associated toxicity; and 4) to determine whether targeted immunosuppression that interrupts immune cell signaling through B7 and/or CD40 ligand (interventions that are likely to be used as adjuncts to gene therapy) affects the development of atherosclerosis in established murine and rabbit models. Accomplishment of the proposed aims will result in generation, validation, and application of new molecular tools for studying vascular biology and improving vascular graft performance. Application of results of these experiments should lead to the development of improved vascular grafts that are resistant to disease and have greatly increased patency rates.